[ui/base;css] adding string template expression replacement

ui/base/template_expressions.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This file defines utility functions for replacing template expressions.
+// For example "Hello ${name}" could have ${name} replaced by the user's name.
+
+#ifndef UI_BASE_TEMPLATE_EXPRESSIONS_H_
+#define UI_BASE_TEMPLATE_EXPRESSIONS_H_
+
+#include <map>
+#include <string>
+
+#include "base/strings/string_piece.h"
+#include "ui/base/ui_base_export.h"
+
+namespace ui {
+
+// Replace ${foo} in the format string with the value for the foo key in
+// |subst|.  If the key is not found in the |substitutions| that item will
+// be unaltered.
+UI_BASE_EXPORT std::string ReplaceTemplateExpressions(
+    base::StringPiece format_string,
+    const std::map<base::StringPiece, std::string>& substitutions);
+
+}  // namespace ui
+
+#endif  // UI_BASE_TEMPLATE_EXPRESSIONS_H_